Description and strategies for best management of

Description and strategies for best management
of Ralstonia solanacearum Race 3 biovar 2 as a
potential incitant of bacterial wilt of tomato
P.G. Champoiseau, J.B. Jones, C. Allen, and T. Momol
24th Annual Tomato Disease Workshop
November 3-5, 2009 State College, Pennsylvania
Who was your speaker?
Patrice G. Champoiseau
Postdoc Research Associate
USDA-NRI project, University of
Florida
pchampoiseau@ufl.edu
Introduction
USDA-NRI Project: Ralstonia solanacearum race 3
biovar 2: Detection, exclusion, and analysis of a select
agent pathogen.
Aim 1. Develop rapid, robust, and reliable diagnostic assays for Ralstonia
solanacearum race 3 biovar 2, using both immunological and DNA-based
approaches.
Aim 2. Identify Ralstonia solanacearum race 3 biovar 2 genes involved in cold
adaptation and growth in plant hosts, using a microarray-based post-genomic
approach.
Aim 3. Develop and deliver a package of optimized education and
management training modules.
Develop evaluation tools to assess program effectiveness.
Outlines
Introduction
Description of the disease
Description of the pathogen
Disease management strategies
Sample submission procedure
Acknowledgements
Introduction
Ralstonia solanacearum is a plant pathogenic
bacterium.
Formerly known as Pseudomonas solanacearum.
Causes bacterial wilts on a wide range of crops,
ornamentals, and weeds.
Worldwide distribution from tropical to warmtemperate areas.
Considered a “species complex” due to significant
variation within the group.
Introduction
Race 1: endemic to the Southern US and causes
bacterial wilt on potato, tobacco, and tomato.
Most severe infections can result in 100% production loss.
Photo: T.M. Momol, UF-IFAS
Introduction
Race 3 biovar 2 (R3b2) subgroup: Select Agent
pathogen in the US.
Probably originated in the tropic highlands (Andes).
Worldwide distribution except US and Canada.
Primary hosts: potato and tomato.
Potato: estimated 1$ billion losses yearly.
Also pathogenic on pepper, tobacco and geranium.
Risk for re-introduction of R3b2 in the US.
Introduction
Pathways for introduction of R3b2 in the US.
Introduction of R3b2 in the US is possible through infected geranium cuttings that are
produced in geographical areas where the pathogen is present.
?
Geranium cuttings
Geranium cuttings
Image source: CAB International, 1999
Race 3 national record
Introduction
Previous introductions resulted in $ millions losses due
to regulatory eradication protocols.
Critical to prevent re-introduction and spread of R3b2 in
the US.
Requires early detection and application of effective
field sanitation practices.
Objective:
Provide description of R3b2 and tomato bacterial wilt.
Describe current diagnosis methods and strategies for
best management of the disease.
Outlines
Introduction
Description of the disease
Description of the pathogen
Disease management strategies
Sample submission procedure
Acknowledgements
Description of the disease
- Wilting of
youngest leaves
Common symptoms
- Wilting and yellowing
of foliage, stunting
- Plant death
Description of the disease
Other symptoms
- Brown discoloration of
vascular tissue
- Stem collapse (young
succulent plants)
Symptoms induced by R3b2 cannot be distinguished from
those induced by race 1 strains
Description of the disease
R. solanacearum is primarily a soilborne and waterborne
pathogen. This figure shows ways of plant infection:
Plant infection
Description of the disease
Pathogen survival
Once established in a field or in the plant, the
bacterium can survive for days to years in:
Description of the disease
Disease epidemiology
Spread of the pathogen from infested to healthy
fields or plants can occur by:
Infested soil
Infested irrigation water
Root contact
Tools and equipment
Outlines
Introduction
Description of the disease
Description of the pathogen
Disease management strategies
Sample submission procedure
Acknowledgements
Description of the pathogen
Diversity: a “species complex”
- 5 races: based loosely on host range.
- 5 biovars: differential ability of strains to produce acid from
a panel of 5 to 8 carbohydrate substrates.
- 4 phylotypes: major genetic groups based on gene
sequence analysis. Reflect the and ancestral relationships
geographical origins of the strains.
- R3b2 strains belong to phylotype II (sequevars 1 and 2)
See Table 1
Description of the pathogen
Culture and identification
- Easy to culture
Mutant
- Optimal growth Temp is
82-90°F
- Individual colonies after
36-48 hours.
- Two colony types:
Wild type (virulent)
Mutant (non-virulent)
Wild type
Description of the pathogen
Culture and identification
- Tetrazolium chloride
(TZC) medium
Wild type (pink center)
Mutant (dark red)
Wild type
Description of the pathogen
R3b2 hosts
Primary hosts
Other cultivated
hosts
Weed hosts
Potato (Solanum tuberosum)
Tomato (Lycopersicon esculentum)
Bean (Phaseolus vulgaris)
Beet (Beta vulgaris)
Bitterground (Momoridica charantia)
Eggplant (Solanum melongena)
Geraniums (Pelargonium spp.)
Peppers (Capsicum spp.)
Bittersweet or climbing nightshade (Solanum dulcamara)
Black nightshade (Solanum nigrum)
Common chickweed (Stellaria media)
Garden nasturtium (Tropaeolum majus)
Horsenettle (Solanum carolinense)
Jimson weed (Datura stramonium)
Lambsquarters (Chenopodium album)
Mustards (Brassica spp.)
Perfoliate blackfoot (Melampodium perfoliatum)
Pinkhead smartweed (Polygonum capitatum)
Purslane (Portulaca oleracea)
Sticky chickweed (Cerastium glomeratum)
Stinging nettle (Urtica dioica)
Whitesnow (Drymaria cordata)
Description of the pathogen
Importance of weed hosts
- Solanum dulcamara
(bittersweet or climbing
nightshade)
- Semi-aquatic weed
- In Europe: responsible
for outbreaks of bacterial
wilt on potato.
Photo: J. Elphinstone, CSL, UK
Outlines
Introduction
Description of the disease
Description of the pathogen
Disease management strategies
Sample submission procedure
Acknowledgements
Disease management strategies
Detection and identification
- Screening tests:
- Plating on semi-selective
medium (SMSA)
See Table 3
Photo: D. B. Langston, UG,
Bugwood.org
- Bacterial streaming
- Immunodiagnostic assays
Disease management strategies
Detection and identification
- Differentiation of biovars
Biovar test is based on
differential ability of strains
to acidify culture media
containing a panel of
carbohydrate substrates.
Disease management strategies
Detection and identification
Several molecular methods can be used to identify R. solanacearum at
the phylotype, sequevar, and biovar level. These methods include:
- PCR-based methods
Identification of the
biovar, phylotype, and
sequevar
- Gene sequencing
Disease management strategies
In locations where the pathogens is present
-
Some level of bacterial control is possible by using a combination
of different control methods in an integrated management strategy:
Host resistance
Grafting onto resistant tomato cultivar
Soil treatment (modification of soil pH, solarization,
application of stable bleaching powder)
Chemical control (soil fumigation and application of
phosphorous acid)
Disease management strategies
In locations where the pathogen is present
Use of chemicals: Thymol and Actigard
A recent experiment conducted
in Quincy in North Florida in
2006 showed that integrated
application of Thymol, a plantderived volatile biochemical, and
Actigard, a plant-resistant
inducer, resulted in significant
reduction in percent of wilted
tomato plants on cultivars that
showed susceptibility to the
disease after artificial inoculation
with the pathogen, as shown on
this figure.
Disease management strategies
In locations where the pathogen is present
- Best strategy for controlling bacterial wilt in the field consists
primarily of phytosanitation and cultural practices, including:
Crop rotation with non-host plants such as grasses,
Intercropping,
Control of weed and root-knot nematode populations,
Planting at non-infested production sites,
Removal of weeds or crop residue where inoculum persists,
Selection of appropriate planting time to avoid heat,
Deep plowing of crop residues,
Satisfactory soil drainage,
Early- and late-season irrigation management
See Table 4
Disease management strategies
In locations where the pathogen is NOT present
- It is critical to prevent introduction and, if inadvertently
introduced, subsequent movement of the pathogen. This is
best achieved with effective cultural sanitation practices :
At the field
Planting only certified disease-free plantlets,
Disinfesting all equipment before moving it between fields,
Controlling floodwater flow, never using surface water for
irrigation.
In the greenhouse
Avoidance of sub-irrigation,
Wide separation of greenhouses from field production areas,
Disinfestations of all frames, trays and tools,
Use of pathogen-free soils or potting mix,
Control of weeds, and limited handling of plants.
Disease management strategies
Disease Management Guide
- Current in formation for
detection, control, containment, and eradication of
R3b2 according to USDA
regulations.
- USDA-APHIS website.
http://www.aphis.usda.gov
Outlines
Introduction
Description of the disease
Description of the pathogen
Disease management strategies
Sample submission procedure
Acknowledgements
Sample submission procedure
Additional resources
Visit our Ralstonia/Bacterial wilt
dedicated website:
Pest and disease management guides
Project description, accomplishments
Real time pest alerts and first reports
worldwide
Protocols, book references and journal
articles database
Web resources
Photo galleries
Access to Ralstonia-L mailing list
http://plantpath.ifas.ufl.edu/rsol/
Acknowledgements
Co-authors.
Caitilyn Allen, Department of Plant Pathology, University of Madison-Wisconsin.
Jeffrey B. Jones, Department of Plant Pathology, University of Florida.
Timur M. Momol, District Extension Director, University of Florida.
Financial support.
National Research Initiative (NRI) program of the USDA Cooperative
State Research, Education, and Extension Services (CSREES).
Acknowledgements
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